Ring current and anisotropy effects on OH chemical shifts in resonance-assisted intramolecular H-bonds

Poul Erik Hansen, Andreas Koch, Erich Kleinpeter

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

Abstract

Ring current effects on resonance-assisted and intramolecularly bridged hydrogen bond protons for 10-hydroxybenzo[h]quinoline 1 and a number of related compounds were calculated and the through-space NMR shieldings (TSNMRS) obtained hereby visualized as iso-chemical-shielding surfaces (ICSS) of various size and direction. These calculations revealed that this through-space effect is comparably large (up to 2 ppm) dependent on the position of the intramolecularly bridged OH proton, and therefore, contribute considerably to the chemical shift of the latter making it questionable to use δ(OH)/ppm in the estimation of intramolecular hydrogen bond strength without taking this into account. Furthermore, the anisotropy effects of additional groups on the aromatic moiety (e.g. the carbonyl group in salicylaldehyde or in o-hydroxyacetophenone of ca. 0.6 ppm deshielding) should also be considered. These through-space effects need to be taken into account when using OH chemical shifts to estimate hydrogen bond strength.
OriginalsprogEngelsk
TidsskriftTetrahedron Letters
Vol/bind59
Udgave nummer23
Sider (fra-til)2288-2292
Antal sider5
ISSN0040-4039
DOI
StatusUdgivet - 3 maj 2018

Emneord

  • Ring current effects
  • Intra molecular hydrogen bonding
  • anisotropy effects
  • Resonance assisted
  • through-space NMR shieldings

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